biotools (version 1.0)

creategroups: Creating Homogeneous Groups

Description

A function to create homogeneous groups of named objects according to an objective function evaluated at a covariate. It can be useful to design experiments which contain a fixed covariate factor.

Usage

creategroups(x, ngroups, sizes, fun = mean, tol = 0.01, maxit = 200)

Arguments

x

a numeric vector of a covariate at which to evaluate the objective function.

ngroups

the number of groups to create.

sizes

a numeric vector of length equal to ngroups containing the group sizes.

fun

the objective function, i.e., to create groups with similar fun; default is mean.

tol

the tolerance level to define the groups as homogenenous; see details.

maxit

the maximum number of iterations; default is 200.

Value

• The value returned is a list of named vectors containing the values for the groups. Also, the result of the objective function evaluated at the covariate x is always printed, as well as the number of iterations required to achieve convergence.

Details

creategroups uses a tol value to evaluate the following statistic: $h = \sum_{j}^{ngroups} abs( t_{j+1} - t_j ) / ngroups$, where $t_j = fun(group_j)$. If $h \leq tol$, the groups are considered homogeneous.

Examples

x <- rnorm(10, 1, 0.5)
names(x) <- letters[1:10]
creategroups(x, ngroups = 2, sizes = c(5, 5))
creategroups(x, ngroups = 3, sizes = c(3, 4, 3), tol = 0.05)

# End (not run)